Institute for Data, Systems, and Society, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, United States.
School of Economics and Management, Tsinghua University, Beijing, 100084, China.
Environ Sci Technol. 2020 Dec 15;54(24):15584-15593. doi: 10.1021/acs.est.0c01381. Epub 2020 Dec 2.
Sustainability policies are often motivated by the potential to achieve multiple goals, such as simultaneously mitigating the climate change and air quality impacts of energy use. Ex ante analysis is used prospectively to inform policy decisions by estimating a policy's impact on multiple objectives. In contrast, ex post analysis of impacts that may have multiple causes can retrospectively evaluate the effectiveness of policies. Ex ante analyses are rarely compared with ex post evaluations of the same policy. These comparisons can assess the realism of assumptions in ex ante methods and reveal opportunities for improving prospective analyses. We illustrate the benefits of such a comparison by examining a case of two energy policies in China. Using ex post analysis, we estimate the impacts of two policies, one that targets energy intensity and another that imposes quantitative targets on SO emissions, on energy use and pollution outcomes in two major energy-intensive industrial sectors (cement, iron and steel) in China. We find that the ex post effects of the energy intensity policy on both energy and pollution outcomes are very limited on average, while the effects of the SO emissions policy are large. Compared with ex ante analysis, ex post estimates of benefits of the energy intensity policy are on average smaller, and differ by location in both sign and magnitude. Accounting for firm-level heterogeneity in production processes and policy responses, as well as the use of empirically grounded counterfactual baselines, can improve the realism of ex ante analysis and thus provide a more reliable basis for policy design.
可持续性政策通常受到多种目标的驱动，例如同时减轻能源使用对气候变化和空气质量的影响。事前分析通过估计政策对多个目标的影响，前瞻性地为政策决策提供信息。相比之下，对可能有多种原因的影响进行事后分析可以回顾性地评估政策的有效性。事前分析很少与同一政策的事后评估进行比较。这些比较可以评估事前方法中假设的现实性，并为改进前瞻性分析提供机会。我们通过研究中国的两个能源政策案例来说明这种比较的好处。使用事后分析，我们估计了两项政策的影响，一项针对能源强度，另一项对 SO 排放实施定量目标，对中国两个主要能源密集型工业部门（水泥、钢铁）的能源使用和污染结果的影响。我们发现，能源强度政策对能源和污染结果的事后影响平均非常有限，而 SO 排放政策的影响很大。与事前分析相比，能源强度政策的事后利益估计平均较小，并且在地点、符号和幅度上都有所不同。考虑到生产过程和政策反应中的企业层面异质性，以及使用基于经验的反事实基准，可以提高事前分析的现实性，从而为政策设计提供更可靠的依据。
